Hsu HC, Lu IC, Lin PH, Dyakov YA, Bagchi A, Lin CY, Hung SW, Lee YT, Ni CK. Does decarboxylation make 2,5-dihydroxybenzoic acid special in matrix-assisted laser desorption/ionization?
RAPID COMMUNICATIONS IN MASS SPECTROMETRY : RCM 2014;
28:1082-1088. [PMID:
24711271 DOI:
10.1002/rcm.6885]
[Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/01/2014] [Revised: 02/20/2014] [Accepted: 03/01/2014] [Indexed: 06/03/2023]
Abstract
RATIONALE
Among the six positional isomers of dihydroxybenzoic acid (DHB), 2,5-DHB is a more favorable matrix for use in matrix-assisted laser desorption/ionization (MALDI) than the other isomers because of its high ion-generation efficiency at 337 and 355 nm. The generation of hydroquinone or p-benzoquinone through the decarboxylation of 2,5-DHB has been suggested to play a crucial role in the ion-generation efficiency of 2,5-DHB.
METHODS
The mass spectra of desorbed neutrals generated from MALDI were measured using electron impact ionization (70 eV) and a quadrupole mass spectrometer and vacuum ultraviolet (118 nm) photoionization and a time-of-flight mass spectrometer. The mass spectra of desorbed ions generated from MALDI were investigated using a time-of-flight mass spectrometer. The dissociation barrier height and dissociation rate of decarboxylation were calculated by an ab initio method and RRKM theory.
RESULTS
Decarboxylation of neutral 2,5-DHB and 2,5-DHB cations was not observed. Theoretical calculations indicated that decarboxylation of neutral 2,5-DHB and 2,5-DHB cations is too slow to occur.
CONCLUSIONS
The high ion-generation efficiency of the 2,5-DHB matrix at 337 and 355 nm is not related to decarboxylation.
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